It’s hard to argue with William Sears’ success. A man whose multiple books have sold millions of copies and been translated into 18 languages is clearly onto something. But it’s not so hard to argue with his science. One of the central warnings in Sears’ work is that babies who cry too much — even those who are left to cry for short periods at night as they learn to go to sleep — could suffer permanent brain damage, leading to a lower IQ, behavioral problems and more. But is there anything behind such a red alert?

Sears makes an extensive case for the brain-damage danger in a heavily footnoted section of his website titled “Science Says: Excessive Crying Could Be Harmful,” in which he cites 19 studies going back 34 years. During periods of panic and anxiety, he explains, adrenaline and the stress hormone cortisol flood the body, preventing brain cells from making healthy connections with one another and leading to developmental and cognitive issues. Of the four studies he cites to back this up, however, two were in rat pups and one was in nonhuman primates. The one that actually involved human babies was a 2004 German study that looked at 70 babies during their first few months in day care. No surprise, the babies experienced stress, and perhaps no surprise either that when researchers took saliva swabs, they found that those babies’ cortisol levels had jumped 75% to 100%.

This study — and those numbers — exploded across the Web after Sears went wide with them and the U.K. paper the Guardian picked up the story, but the researchers who did the work sounded no such alarm. For one thing, in nearly half the toddlers, cortisol levels fell in as little as 30 minutes, and all of them acclimated readily in time. What’s more, while the investigators acknowledge that extreme doses of cortisol can harm brain tissue, that was not likely happening in these cases. “There is no evidence, as yet,” they wrote, “that small elevations within the ranges observed here have adverse consequences. [W]e cannot conclude that the stress associated with transition to childcare has either positive or negative consequences.”

Antisocial behavior, poor school performance and a tenfold increase in the risk of ADHD are also the dangers babies face if their parents don’t respond immediately to their cries, according to Sears, and he cites a number of studies — particularly one from Pediatrics and one from Infancy, both conducted in 2002, and one from Archives in Disease in Childhood from 2004 — to buttress that claim. But all three of those studies dealt with babies suffering from colic or, worse, a condition known simply as persistent crying, which goes on even longer than the 12 weeks colic usually lasts. In those cases, it’s the very inconsolability of the crying — despite parental soothing, feeding, rocking, singing, pacing, changing and pleading — that defines the condition. Indeed, the studies go out of their way to absolve the parents of any blame for this.

“Our findings provide evidence that the quality of maternal behavior appears to be unrelated to this effect,” noted one of the 2002 studies. The 2004 study similarly found no differences in the home environments of prolonged criers and other kids. Instead, the researchers argue that the crying is just a symptom of an underlying condition — perhaps neurological — that also causes later cognitive or behavioral issues. Just as your fever is not responsible for your cold, so too is the crying not behind the developmental problems.

Most troubling is the way Sears seems to conflate the circumstances of severely abused or neglected babies with those whose parents merely let them cry occasionally. Psychologist Alicia Lieberman of the University of California, San Francisco, whose 1995 study Sears cites, takes particular exception to that. The paper’s content, she said in an e-mail to TIME, “is not relevant to the argument he makes because my work involves babies and young children whose parents are in the pathological range of neglect and maltreatment … not children with normative, ‘good-enough’ parenting.”

Psychologist Joan Kaufman of Yale University, whose 2001 paper was also cited by Sears, echoes that. “Our paper,” she wrote via e-mail, “is not referring to routine, brief stressful experiences, but to abuse and neglect. It is a mis-citation of our work to support a non-scientifically justified idea.”

None of this means that Sears’ larger philosophy of attachment parenting is fatally flawed — as his millions of believers and their happy, well-adjusted babies would surely attest. But winning followers with the soundness and sweetness of your arguments is very different from scaring them into line with warnings of things that will never happen. Parenting, for all its transcendent joys, is already tough enough.